1. Field of the Invention
The present invention relates to a digital integrated circuit for the color matrix of a color-television set with digital signal processing circuitry wherein the digital luminance signal and the two digital color-difference signals are applied to the three parallel inputs of the color matrix, whose three parallel outputs provide the digital color signals.
2. Description of the Prior Art
In present-day color-television systems (NTSC, PAL, SECAM), the luminance signal Y is composed of the three color signals R=red, G=green, and B=blue according to the following equation: EQU Y=0.3R+0.59G+0.11B.
The color-television transmitter transmits the two color-difference signals R-Y and B-Y together with further signals using different modulation methods depending on the color-television system. After demodulation and separation, the color signals are regained by the color matrix in the color-television receiver according to the following equations: EQU R=(R-Y)+Y EQU G=-0.5(R-Y)-0.19 (B-Y)+Y EQU B=(B-Y)+Y
For the color matrix commonly used in color-television sets, circuits consisting of suitable resistor networks are generally used which convert the analog color-difference signals into corresponding analog color signals.
In color-television sets with digital signal processing circuitry, as are disclosed, for example, in Offenlegungsschrift DE No. 28 54 236 A1 corresponding to U.S. Pat. No. 4,270,139, the color-difference signals and the luminance signal are present in digital form, and in such sets, too, a digital color matrix must satisfy the above three equations for the digital color signals. By means of parallel adders and parallel multipliers, the idealized digital color matrix can be readily implemented on the basis of these equations.
However, the use of such a color matrix would be greatly limited because such a matrix would not take into account the decimal reduction factor 0.88 for the red-minus-luminance signal and the decimal reduction factor 0.49 for the blue-minus-luminance signal and, in addition, would leave the manufacturer no choice in determining the color overload.